Note: the original title Solar Neutrons and the 1970s cooling period was unintentionally misleading as Dr. Svalgaard points out in comments:
What produces Solar Neutrons?
the title of the post is misleading. The cosmic rays are protons, not neutrons, and are not produced by the Sun, but by supernovae in the Galaxy. The ‘neutrons’ are produced in the Earth’s atmosphere when cosmic ray protons collide with air.